My Sport Design

I invite comments, suggestions on this sports design I've been working on. Plan view only at this stage.

I really like the outlines. If those are fixed flaps, I'd suggest losing them, and making a real tapered wing. Not that hard to do, better warp resistance, more efficient, lighter and cheaper. The airfoil looks pretty thin? For light balsa and a possible source of low pitch props, check with Peter Lloyd in Vic. http://www.pelaero.com.au/ Steve

http://www.nwskyraiders.com/index.html

For Danny Dirt:

Sorry I should have included some specs.

Power : Taipan .15

WING
Section : E472 (with extended flap)
Span : 979 mm (between centre of tips)
Area : 16 dm^2 (includint flap)
Aspect Ratio : 6
Flap : 4 dm^2 (25%)

Moment Arm : 324 mm AC Wing to Ac Tailplane

TAILPLANE
Span : 386 mm (at hinge line)
Area : 2.97 dm^2 (18.5%)
Aspect Ratio : 5
Stab/Elev : 55%/45%

Moveing Flap to regain lift from thin E472 section. This section is 12% but Cl max = 1.25 at Re 300000 rather high for a thin section and has a wide drag bucket (see NASG airfoil database).

What speeds are you planning on flying? At 65-70 mph+(104-112 kph) a 12% wing should have no problems but at lower stunt type speeds of 50-55 mph (80-88 kph) I'd choose a thicker 20-24% airfoil. While the max CL of the thicker wing usually isn't as great (the graphs I've seen are plotted for Reynolds numbers in the 1,000,000+ range) the lift dropoff at stall is much gentler and (near)max lift occurs over a wider range.

It looks kinda small for a good 15. The Taipan can probably easily handle 50% more wing area. A thin airfoil(12%or less) requires either very low weight, a large wing, or high speed. Anything less than 15% thick definitely gets less happy with a wing loading over 4.8cm2/gm.(hope I got those metric conversion right!!)

The tail/wingarea look good. Be prepared to shorten the tail if needed to get the balance point right.

Will your tank work?
It appears to set above the leading edge of the wing.
Will this allow you room for adjustment?

Hi

As far as speed goes, I expect it to be faster than what I am flying now, 110 kmph. It all depends on the prop. My intention is to step up speed as I get used to it by change props.

I am currently running an 8 x 4 prop and getting 110 kmph. The recommended prop is 7x6 so as a very rough estimate 110/4*6 = 165 kmph. On top of this, the motor would be reviving out into it's power band so likely to be faster than this. Think I might need longer lines.

I have not totally settled on the wing profile yet, I may still use a thicker section or build 2 versions. It is a little difficult to predict turning performance as I don't have polars for this kind of flap arrangement but I am expecting a min turning radius of around 3 metres or so.

Due to the rear exhaust and tank position, the wing will be below the thrust line, just enough to clear the muffler and tank. The engine has to be in this position, close to the wing for natural balance. I don't like adding tail weight as mass in the extremities opposes responsiveness to control. Remember it is not a comp stunter but intended to be a fast sports plane for fun.

Attached image of a trainer. The profile view would be something like this.

OK The section is probably a bit thin.
How about Eppler 473, 16% thick at 20% of chord.
Eppler 472 is 12% at 18% of chord. The forward position of the max thick point seem to produce very heigh lift for thin sections.
Interestingly Xfoil seems to underestimate Cd and Cl max compared with measured tests.

The wing area size of my model is based on 2.5cc stunters form my youth and also efficiently using stock balsa sheet. I take the point the Taipan probably needs a bigger plane or thicker wing.

What are the pros and cons of extended flaps like these to flaps incorporated into the wing profile?

How do most CL stunters do moving flaps these days?